不同放牧方式对阿拉善左旗主要草场类型群落特征和土壤养分的影响

为探究不同放牧方式对阿拉善左旗草场的影响,本试验选取绵刺（Potaninia mongolica）、梭梭（Haloxylon ammodendron）、红砂+藏锦鸡儿（Reaumuria soongorica+Caragana tibetica）和红砂+珍珠猪毛菜（Reaumuria soongorica+Salsola passerina）4种主要的草场类型,分析长期禁牧、2016年政策允许开始放牧及长期放牧3种放牧方式下草场群落数量特征、群落物种多样性和土壤养分的差异。结果表明：禁牧对于草场植被恢复有显著效果,但长期禁牧会降低群落物种多样性;长期禁牧后于2016年开始放牧的草场生长状况更好,群落的高度、盖度、密度和生物量等数量特征显著提高,并且改善了土壤养分状况。综上所述,阿拉善目前所制定的禁牧与放牧相结合的放牧利用方式是科学合理的,既能保护草地又可获得经济收益。     

人为干扰对福建建瓯常绿阔叶林物种组成 及其数量特征的影响

【研究目的】以建瓯万木林常绿阔叶林(C)和人为破坏阔叶林(D)为对象分析人为干扰对群落物种组成及其数量特征的影响;【方法】野外调查样方植物种、个体数、植株高度、胸高直径、冠幅(盖度)和生活型,分析重要值、频密值及群落优势度;【结果】干扰后D群落物种更丰富;C群落演替已达到相对稳定阶段,D正在形成物种更为丰富的典型当地地带性植被类型;木荷和罗浮栲在C和D群落中都具有最大重要值;C群落喜阴植物种类较多,D群落则以阳性和中性植物种类较多;垂直高度3m以下的层次,D群落重要值(或频密值)较为平均地分配到各物种上;D群落稳定性较C差;【结论】一定程度的人为干扰与封山育林相结合是维持甚至增加群落物种多样性的有效手段;干扰群落经封山育林向典型地带性植被类型演替。     

Discharges Between Discrete Water Drops on the Silicone Rubber Sruface and Reason Unkown Flashover

During data collection,the experimental data such as curve of force versus displacement are usually disturbed by the environmental uncertain signals,which cause the data to drift greatly.Since the drift is stochastic,uncertain,and has distorted the real experimental curve severely,it brings lots of difficulties in analyzing the experiment results.In this paper,based on the characteristic of the stochastic disturbance signals,a three-phase digital filter arithmetic is given,in which the disturbance signals are filtered in each phase gradually,according to the different filter methods,and then the real curve is reappeared again.Two idiographic and different instances are adopted to prove the validity of the arithmetic at the end.     

Physiological and reproductive consequences of human disturbance in Humboldt penguins: The need for species-specific visitor management

Over the last decade the Humboldt penguin, Spheniscus humboldti, has become a focus for ecotourism. Current management applies visitor guidelines similar to those developed for Magellanic penguins, Spheniscus magellanicus. However, unlike these, Humboldt penguins are extremely sensitive to human presence. Breeding success was significantly reduced at frequently visited sites. Heart rate telemetry during disturbance experiments revealed that Humboldt penguins respond more strongly to human presence than do any other penguin species thus far studied. A person passing an incubating penguin at 150 m distance already provoked a significant heart rate response. Recovery times were up to half an hour after direct human approach, causing increased energy expenditure without any overt behavioural reaction. Being extraordinary sensitive to human activity with little habituation potential the Humboldt penguin proves to be a difficult focal species for ecotourism. For sustainable ecotourism visitors are required to stay out of sight of Humboldt penguin breeding and moulting areas. Management guidelines need to acknowledge that even closely related species may react very differently towards human presence.     

Rapid decline of the volcanically threatened Montserrat oriole

Prior to 1995, the Montserrat oriole (Icterus oberi) was confined to ca. 30 km² of hill forest on the Lesser Antillean island of Montserrat, but was not listed as globally threatened. Since then, the eruption of the Soufriere Hills volcano has destroyed more than half of the species’ range. Recent intensive monitoring has indicated that the species has also declined dramatically within the remaining intact forest, and is now critically threatened. Different monitoring and analytical methods indicate a decline of 8-52% p.a., and a remaining global population of ca. 100-400 pairs. This case study justifies the use of the restricted range criterion in designating threatened species. Despite intensive monitoring and the use of several analytical methods, it has proved surprisingly difficult to estimate the magnitude of the oriole’s decrease, or to control for potential artefacts in the census method. We discuss the reasons for this. The cause(s) of population decline in the intact forest are unclear, though two hypotheses appear plausible: a decrease in arthropod food, a result of volcanic ash fall, and an increase in nest predation as a result of increases in populations of opportunistic omnivores.     

The tripartite symbiosis between legumes, rhizobia and indigenous mycorrhizal fungi is more efficient in undisturbed soil

We investigated how the rate of colonization by indigenous arbuscular mycorrhizal fungi (AMF) affects the interaction between AMF, Sinorrhizobium meliloti and Medicago truncatula Gaertn. To generate a differential inoculum potential of indigenous AMF, five cycles of wheat, each of 1 month, were grown in sieved or undisturbed soil before M. truncatula was sown. The early colonization of M. truncatula roots by indigenous AMF was faster in undisturbed soil compared with sieved soil, but by pod-fill the frequency of hyphae, arbuscules and vesicles was similar in both treatments. At this latter stage, M. truncatula grown in undisturbed soil had accumulated a greater biomass in aboveground tissues, had a greater P concentration and derived more N from the atmosphere than plants grown in disturbed soil, although soil compaction resulted in plants having a smaller root system than those from disturbed soil. The difference in plant P content could not be explained by modifications in hydrolytic soil enzymes related to the P cycle as the activity of acid phosphatase was greater in sieved than in undisturbed soil, and the activity of alkaline phosphatase was unaffected by the treatment. Thus, the results observed were a consequence of the different rates of AMF colonization caused by soil disturbance. Together with earlier results for soybean, this study confirms that soil disturbance modifies the interaction between indigenous AMF, rhizobia and legumes leading to a reduced efficacy of the bacterial symbiont.     

Density and success of bird nests relative to grazing on western Montana grasslands

Grassland birds are declining at a faster rate than any other group of North American bird species. Livestock grazing is the primary economic use of grasslands in the western United States, but the effects of this use on distribution and productivity of grassland birds are unclear. We examined nest density and success of ground-nesting birds on grazed and ungrazed grasslands in western Montana. In comparison to grazed plots, ungrazed plots had reduced forb cover, increased litter cover, increased litter depth, and increased visual obstruction readings (VOR) of vegetation. Nest density among 10 of 11 common bird species was most strongly correlated with VOR of plots, and greatest nest density for each species occured where mean VOR of the plot was similar to mean VOR at nests. Additionally, all bird species were relatively consistent in their choice of VOR at nests despite substantial differences in VOR among plots. We suggest that birds selected plots based in part on availability of suitable nest sites and that variation in nest density relative to grazing reflected the effect of grazing on availability of nest sites. Nest success was similar between grazed plots and ungrazed plots for two species but was lower for nests on grazed plots than on ungrazed plots for two other species because of increased rates of predation, trampling, or parasitism by brown-headed cowbirds (Molothrus ater). Other species nested almost exclusively on ungrazed plots (six species) or grazed plots (one species), precluding evaluation of the effects of grazing on nest success. We demonstrate that each species in a diverse suite of ground-nesting birds preferentially used certain habitats for nesting and that grazing altered availability of preferred nesting habitats through changes in vegetation structure and plant species composition. We also show that grazing directly or indirectly predisposed some bird species to increased nesting mortality. Management alternatives that avoid intensive grazing during the breeding season would be expected to benefit many grassland bird species.     

Dolphin-watching tour boats change bottlenose dolphin (Tursiops truncatus) behaviour

Over the last decade there has been considerable growth in marine mammal-watching tourism throughout the world. Due to the species use of coastal habitats, bottlenose dolphins are most frequently exposed to dolphin-watching tourism. We conducted boat-based focal follows of schools of bottlenose dolphins to determine the effect of boats on dolphin behaviour. A CATMOD analysis showed that behaviour differed by boat number, in particular, resting behaviour decreased as boat number increased. Dolphins rested less and engaged in more milling behaviour in the presence of permitted dolphin-watching boats compared to non-permitted boats. An increase from 49 to 70 permitted trips per week and a change in their departure times resulted in a further decrease in resting behaviour. Currently the effects of boats, in particular permitted boats, on dolphin resting behaviour whilst they are in the Bay of Islands, are substantial. In the light of these findings we suggest that current legislation in New Zealand is not affording this isolated population protection from disturbance.     

滹沱河岗黄段湿地人类活动影响评价研究

滹沱河岗黄段湿地是北方干旱缺水地区典型的河湖湿地,其影响因子可分为自然因子与人为因子。采用层次分析模型,从生态环境、生产特征、污染物排放、环境管理4个方面,分析评价了人类活动对岗黄湿地的影响状况以及影响的主要途径与方式,并提出了主要的湿地保护措施。